The Research Of Drift Detection And Correction Technology Of The Electro-optic Modulator's Bias Voltage

Mach-Zender(M-Z) optical modulator(EOM) has been used as a result of its own structural constraints, which is vulnerable to the interference of its own temperature and environment, resulting in the performance of its work is not stable. In this paper, we study the detection and automatic control system of electro optic modulator bias voltage drift in laser communication system. This design uses the perturbation method, that is, the bias voltage of the electro-optic modulator is superimposed on a small low frequency perturbation signal which does not affect the system operation,then the output of the signal is modulated by an electro optic modulator,and multiply with the original disturbance signal, By the result of the multiplication, the amount of direct voltage can be obtained by including the size of the offset and the information of the direction, The positive and negative direction of the straight flow, the size of the direct flow is proportional to the offset distance.As the direct voltage, the PID controller can be used as the error signal to realize the correction of the working point. In this design, we propose a method of AD630 based on the phase locked amplifier, which can recover the offset signal from 100 dB interference noise and output the results with the reference signal. Experimental results show that when the circuit is used for pulse modulation, the extinction ratio of the electro-optic modulator is less than or equal to 0.32 dB, which greatly improves the working stability of the electro-optic modulator.